Investment in 111 West 57th Partners LLC (Details)	1 Months Ended	3 Months Ended			6 Months Ended
	Jul. 31, 2015 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2014	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	May 31, 2016 USD ($)	Jun. 28, 2013 USD ($) ft²
Schedule of Equity Method Investments [Line Items]
Company's aggregate initial investment											$ 57,250,000
Company's aggregate initial membership interest percentage											60.30%
Other members and Sponsor initial investment											$ 37,750,000
Approximate gross square feet of project | ft²											346,000
Term of loan					4 years
Extension option of loan					1 year
Annaly CRE LLC initial mortgage and acquisition loan repaid							$ 230,000,000
Distribution attributable to Company's investment	$ 11,699,000
Distribution retained by the Company, net of amounts repaid to Capital LLC	1,831,000
Description of partnership agreement distribution					The JV Agreement and related operating agreements generally provide that all distributable cash shall be distributed as follows: (i) first, 100% to the members in proportion to their percentage interests until Investment LLC has received distributions yielding a 20% internal rate of return as calculated; (ii) second, 100% to the Sponsor as a return of (but not a return on) any additional capital contributions made by the Sponsor on account of manager overruns; and (iii) thereafter, (a) 50% to the members in proportion to their respective percentage interests at the time of such distribution, and (b) 50% to the Sponsor.
Subordinated participation interest to CEO				10.00%
Percentage of distribution on company's initial investment to be received prior to CEO receiving percentage distribution				150.00%
Capital contributed by Capital LLC	$ 9,868,000
Capital contributions					$ 0
Valuation of shortfall capital contribution as multiple of amount actually contributed					1.5
Sponsor calculation of investment LLC aggregate investment percentage after dilution					48.00%
Difference between the Company's carrying amount and the underlying equity		$ 867,000			$ 867,000
Impairment on the Company's equity method investments					0
Assets [Abstract]
Real estate held for development, net		635,676,000			635,676,000				$ 563,133,000
Escrow deposits		9,250,000			9,250,000				9,000,000
Other assets		14,374,000			14,374,000				6,908,000
Total assets		659,300,000			659,300,000				579,041,000
Liabilities [Abstract]
Loans payable		518,961,000			518,961,000				441,749,000
Other liabilities		19,876,000			19,876,000				16,788,000
Total liabilities		538,837,000			538,837,000				458,537,000
Equity [Abstract]
Total members' equity		120,463,000			120,463,000				120,504,000
Total liabilities and members' equity		659,300,000			659,300,000				$ 579,041,000
Income (Loss) [Abstract]
Rental income		0	$ 0		0	$ 0
Expenses		10,000	179,000		41,000	829,000
Net income (loss)		(10,000)	$ (179,000)		(41,000)	$ (829,000)
Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Additional borrowing required to complete project		60,000,000			60,000,000
Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Additional borrowing required to complete project		$ 100,000,000			$ 100,000,000
Capital LLC [Member]
Schedule of Equity Method Investments [Line Items]
Percentage of outstanding shares to be owned by CEO					20.00%
Investment LLC [Member] | Capital LLC [Member]
Schedule of Equity Method Investments [Line Items]
Terms of distributions to Capital LLC					available cash of Investment LLC will be distributed first to Capital LLC until it has received a 20% internal rate of return (calculated as provided for in the JV Agreement as noted above), second to the Company until it has received 150% of its capital, and; thereafter, available cash is split 10/90 with 10% going to Mr. R.A. Bianco as the subordinated participation interest noted above and 90% going to Capital LLC and the Company pari-passu, with Capital LLC receiving one-half of its pro-rata share based on capital contributed and the Company receiving the balance.
Line of Credit [Member] | R. A. Bianco [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity								$ 10,000,000		$ 1,000,000
AIG [Member]
Schedule of Equity Method Investments [Line Items]
Financing obtained by 111 W 57th Partners							400,000,000
Apollo [Member]
Schedule of Equity Method Investments [Line Items]
Financing obtained by 111 W 57th Partners							$ 325,000,000
Junior Mezzanine Loan [Member]
Schedule of Equity Method Investments [Line Items]
Junior mezzanine loan sold by lender to an affiliate of Spruce Capital Partners LLC					$ 25,000,000